Determination ofl-Ascorbic Acid and Total Ascorbic Acid in Vascular and Nonvascular Plants by Capillary Zone Electrophoresis

Abstract

A capillary zone electrophoresis (CZE) procedure for the determination ofl-ascorbic acid (AA) and total ascorbic acid (TAA, as the sum of AA and dehydroascorbic acid) in vascular plants, lichens, bryophytes, and liverworts is described. The samples were frozen in liquid nitrogen and extracted with 2% metaphosphoric acid. To determine AA, an aliquot was directly injected in a fused-silica capillary. The determination of TAA was performed upon its reduction withdl-homocysteine at pH 7. The background electrolyte contained 60 mM sodium chloride, 60 mM sodium dihydrogen phosphate, 1 × 10−4% hexadimetrine bromide, and NaOH up to pH 7. The procedure was rapid and highly reproducible; the limit of detection was 0.2 μg ml−1, which corresponded to 0.4 mg/100 g of sample. The method was validated by comparison with an enzymatic assay. While the enzymatic assay failed to quantify AA in some plants owing to strong background UV absorption, CZE was successful in all the extracts assayed.